The present invention is directed to a novel planar structure GaAs electro-optic transmitter-receiver and to the method of fabrication. High speed low cost fiber optic communication systems will require a monolithic electro-optic transmitter-receiver. GaAs depletion mode MESFET logic is integratable with an AlGaAs-GaAs laser diode to form the transmitter of a fiber optic communication system.
In the prior art there has been described the growth of N type AlGaAs, GaAs, and AlGaAs layers successively on a semi insulating GaAs substrate for a semiconductor laser device such as shown in the U.S. Pat. Nos. 4,105,955, 4,166,278 and 4,183,038.
In the present invention a channel or depression is formed in the planar surface of a semi-insulating GaAs substrate; the channel is substantially filled with successive epitaxial layers of AlGaAs, GaAs, AlGaAs and GaAs which form the optoelectronic component (i.e. the transverse junction stripe laser or the detector), the surface of which top epitaxial layer is coplanar with (or substantially coplanar with) the substrate planar surface. The adjacent planar surface of the semi-insulating GaAs substrate contains cooperating MESFET electronics preferably fabricated by direct ion implantation. This placing of both the electrical and optical components on or at the planar surface simplifies processing steps and facilitates fabrication and testing.